Conventional air intake manifolds used on internal combustion engines in vehicles are made of cast iron or heavy wall aluminum. In order to save weight, and thus improve fuel economy, the materials that intake manifolds are being revised. For these materials to maximize the weight savings, they should use thin wall metals, such as aluminum or magnesium, and plastic, such as molded glass reinforced nylon materials. One concern, however, when designing air induction systems is the potential for induction backfires. The pressure spikes from an induction backfire can exceed 150 pounds per square inch in 10 micro-seconds, which could result in component damage to the induction system. Cast iron or heavy wall aluminum can generally absorb this pressure without permanent deformation or cracks forming. These lighter materials are generally not as robust in absorbing internal positive pressure spokes caused by an induction backfire as is the conventional steel material. Thus, the ability of these intake manifolds to sustain the internal pressure from possible sudden bursts of air due to engine back pressure, without being damaged, is significantly reduced. A possible solution is to dimension the wall thickness such that a sudden increase in positive pressure within the manifold can be absorbed without damage to the intake manifold. However, the increased weight and cost of such a design are undesirable.
Implications of failures due to backfires are non-reparable components, in which repairs will require expensive component replacement; and potential damage to surrounding components in the vehicle's engine compartment which also see the pressure spokes such as throttle bodies, air cleaners and clean air tubes.
Therefore, in order to use the new lighter materials to save weight, the need arises for a way to handle the possible back pressure without damaging the air intake manifold, which is expensive to replace. Thus, a desire exists to use thin walled, light weight materials for the manifold, in which a sudden pressure increase can be absorbed without damage to the overall intake manifold. If the lighter weight manifolds are made to generally withstand pressures from induction backfires with minimal damage and expense, then they will be economical to use.